Projection system employing adjustable mirror for image framing

ABSTRACT

A photographic projection system employing an oversize projection aperture and adjustable mirror configured for displacement of the projection path relative to the projection screen so as to frame the projected image within the screen border and thereby transmit only the recorded image of the film to an observer. In a preferred embodiment, the system is a rear projection viewer having a projection lens assembly configured for projecting an image of a film section to an adjustably mounted mirror element and from the latter to the rear of a transparent, front-viewing screen. The projection lens assembly is adapted to project an image of a film section which exceeds the area of the recorded image-frame, and the viewing screen includes an opaque border element which conforms to the projected size of the image-frame such that displacement of the mirror element adjusts the projection path relative to the screen and frames the projected image within the screen border.

United States Patent 1191 Young PROJECTION SYSTEM EMPLOYING ADJUSTABLEMIRROR FOR IMAGE FRAMING [75] Inventor: Richard W. Young, WellesleyHills,

Mass.

[73] Assignee: Polaroid Corporation, Cambridge,

' Mass.

[22] Filed: Dec. 6, 1971 [21] Appl. No.: 204,869

52 US. Cl. 352/129, 352/160 51 Int. Cl. G03b 21/00, G03b 21 /46 58 Fieldof Search 352/104, 129, 119, 160

[56] References Cited UNITED STATES PATENTS 1,596,012 8/1926 Gauriat352/194 X 2,576,586 11/1951 Franke1.... 352/119 1,204,771 11/1916Hopkins 352/119 2,278,781 4/1942 Harrison 352/119 3,582,195 6/1971Pignone 352/104 X Feb. 12,1974

Primary ExaminerMonroe H. Hayes 7 Attorney, Agent, or FirmRobert F. Peck[57] ABSTRACT A photographic projection system employing an oversizeprojection aperture and adjustable mirror configured for displacement ofthe projection path relative to the projection screen so as to frame theprojected image within [the screen border and thereby transmit only therecorded image of the film to an observer. In a preferred embodiment,the system is a rear projection viewer having a projection lens assemblyconfigured for projecting an image of a film section to an ad justablymounted mirror element and from the latter to the rear of a transparent,front-viewing screen. The projection lens assembly is adapted to projectan image of a film section which exceeds the area of the recordedimage-frame, and the viewing screen includes an opaque border elementwhich conforms to the projected size of the image-frame suchthatdisplacement of the mirror element adjusts the projection path relativeto the screen and frames the projected image within the screen border.

1 Claim, 4 Drawing Figures PAH-:NTED FEB1 2l974 FIG. I

FIG. 4

a R w m a W T mm W D a j w mw m%% N PROJECTION SYSTEM EMPLOYINGADJUSTABLE MIRROR FOR IMAGE FRAMING BACKGROUND OF THE INVENTION 1. Fieldof the Invention This invention relates to photographic projectionsystems and more particularly to a motion picture projection systemhaving improved image framing.

2. Description of the Prior Art In photographic systems of the priorart, as for example, in motion picture projection systems with whichthis application is particularly concerned, image framing is provided bypositioning the recorded image of the film in registration with aconforming opening in the aperture plate. Hence, the latter provides anopaque border encompassing the recorded image and thereby transmits toan observer, a projected image respresentative of this recorded image.The lateral position of the recorded images on the film strip, iscontrolled by film side guides etc. in the camera and is substantiallyconsistent from film to film. Hence, lateral registration of the imageswith the aperture of the projector is easily achieved by similar sideguides. However, since the longitudinal position of the images relativeto the film sprocket holes varies from film to film, projector apparatusof the piror art generally provide for manual adjustment of the clawposition with respect to the aperture plate for image framing. Inasmuch,as the claw is typically designed for reciprocating motion adapted toincrementally advance the film, the desired manual adjustment generallyrequires a cumbersome mechanical arrangement which results in increasedcomplexity and cost. A I

Accordingly, it is an important object of this invention to provide animproved projection system.

Another primary object of this invention is to provide an improvedprojection method and system providing image framing in accordance withadjustment of the optical projection path.

A further object of this invention is to provide a compact rearprojection apparatus having a simplified framing mechanism.

SUMMARY OF THE INVENTION The apparatus of the invention, which in itsillustrated embodiment is particularly adapted for projection of motionpicture film, comprises image projection means for projecting imagebearing rays from a film section along a given path, framing meansinterposed in said path for intercepting marginal portions of theprojected image so as to provide a border therefor, and means interposedbetween said image projecting means and said framing means forredirecting the optical path of said image bearing rays relative to saidframing means so as to locate a given portion of the image of such filmsection within said framing means.

In the preferred embodiment, the invention is embodied in a rearprojection viewer including a projection lens assembly which isconfigured to project an image of photographic film along a given pathto a pivotally mounted mirror element and from it to the rear of a frontviewing screen. The projection lens assembly projects an image of asection of film in excess of a given film frame and the transparentscreen is framed within an opaque border which. substantially conformsto the projected size of thefilm frame such that adjustment of themirror element to displace the projection path relative to the viewingscreen serves to locate the imageof the film frame within the screenborder, and consequently, displays only image portions representative ofthe film frame to an observer.

BRIEF DESCRIPTIONOF THE DRAWINGS The novel features that are consideredcharacteristic of the invention are set forth with particularity in theappended claims. The invention itself, however, both as to itsorganization and its method of operation together with additionalobjects and advantages thereof will best be understood from thefollowing description of the preferred embodiment when read inconnection with the accompanying drawings wherein like numbers have beenemployed in the different figures to denote the same parts and wherein:

FIG. 1 is a diagrammatic view in section of a motion picture viewerembodying the features of this invention;

FIG. 2 is a view in perspective view of the apparatus shown in FIG. 1;

FIG. 3 is a fragmentary view in elevation of the mirror arrangementshown in FIG. 1, and

FIG. 4 is a fragmentary plan view illustrating the relationship betweenthe photographic film and the projection lens assembly shown in FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGS. 1 and 2, thephotographic projection system of the present invention preferably takesthe form of a rear projection view 10 comprising a boxlike housing 12defined in part by a viewing screen 14. Positioned rearwardly of screen14 and in adjoining relation to the top surface 16 of the housing 12, is'a cassette-receiving well 18 which is adapted to hold a motion picturefilm cassette 20 as shown in FIG. 1. Pivotally mounted at the forwardedge of the well 18 is a door member 24 which controls access to thecassette well. I

The cassette 20, which may for example, be a multipurpose cassette suchas described in the copending application Ser. 813,469 of Rogers B.Downey filed on Apr. 4, 1969, now issued on Sept. 28, 1971 as U.S. Pat

No. 3,608,455 which is designed for exposure process-- ing andprojection without removal of the film strip from the cassette,comprises a generally flat parallelepiped casing enclosing a pair ofmotionpicture film spools 26 and 28 upon which a motion picture film 30is disposed for transport between one spool and the other, in anarrangement where portions of the film are advanced across a cassetteopening 34 which facilitates projection of the images recorded on thefilm.

In this cassette, the opening 34 serves to facilitate both exposure andprojection inasmuch as it permits image bearing light rays to impinge onincremental sections of the film strip 30 progressively presentedthereat so as to facilitate exposure and subsequently to permit lightrays from an external source (not shown) to be directed through theincremental sections outwardly of the cassette to facilitate projectionoperations. For the latter operation, means are also provided in thecassette 20 for permitting entrance of suitable illumination and forredirecting such illumination in a downward direction through the film30 and out of the opening 34. For example, an opening or aperture 36 isprovided in one side wall of the cassette 20 and, a reflector element(not shown) such as a mirror or prism is included within the cassette toredirect light, entering aperture 36, through the incremental sectionsof the film 30 and out of the cassette opening 34. Hence, a conventionalilluminating means (not shown) such as a projection lamp or the like ismounted in the viewer apparatus so as to suitably direct illuminationinto the aperture 36. Further, the cassette 20 includes a support plate(not shown) mounted behind the film 30 in adjoining relation to theopening 34 which is adapted to cooperate with an aperture plate 42 ofthe projector .10 to slidably engage the film and locate it in theprojection plane.

Also included within housing 12 in adjoining relation to thecassette-receiving well 18 are means (not shown) for driving the spools26 and 28 and for advancing film 30 across opening 34. For example,appropriate drive shafts (not shown) are adapted to engage the spools 26and 28 so as to suitably rotate them, and a conventional clawarrangement 40 shown in FIG. 1 is adapted to engage the film sprocketholes 37 (shown in FIG. 4) so as to intermittently advance the film 30across the opening 34.

Mounted beneath the cassette-receiving well 18 and in registration withthe cassette opening 34 is the aperture plate 42 and a lens assembly 44which are configured to project a beam of light 45, transmitted from thecassette opening 34, vertically downward along an optical axis 46 to areflecting means, such as a mirror element 48, and from the latter alonga second projection path 50 to the rear 52 of the transparent screen 14.In the illustrated embodiment, a particularly compact viewer employing asingle mirror and tilted viewing screen such as described in thecommonly assigned copending application Ser. No. 174,373 of Philip G.Baker et al, filed on Aug. 19, 1971 is employed. In this embodiment,the' mirror 48 in its center position in inclinecl'at an angle ofapproximately 34 to the horizontal and hence redirects the'beam from theoptical axis 46 along the second axis 50 which is inclinedbyapproximately 22 to the horizontal as shown. The front viewing screen14 -is disposed p'erpendicular to this axis 50 and includes means forredirecting its transmitted or viewed image slightly downward incompensation for the upward'inclination of this axis 50. Thisarrangement economically provides a highly compact viewer whole profileas viewed from the front of the unit is essentially determined by thescreen size.

In the apparatus of the invention, the aperture plate 42 and the lensassembly 44 are adapted to project an image of section of film strip (aslater explained in detail in regards to FIG. 4) which exceeds the areaof the film frame or scene recorded on the film strip 30. In conjunctionwith this projection of an oversized film section, the transparentscreen 14 is encompassed by and retained within a mask-like opaqueborder 70, which is substantially equal or slightly less than the areaof the projected image of the scene, and hence, is configured tointercept marginal portions of the projected beam 45 and thereby framethe image transmitted to an observer. Herein, the film frame image isdefined as the image of the scene previously recorded on the film by thecamera. The projection image is defined as that image formed by thecross section of the projection beam taken at a given plane and, inaccordance with the invention, is greater in area than the projection ofthe scene when viewed in that plane. Finally, the viewed image isdefined as that portion of the projection beam which is transmitted toor seen by the viewer. In accordance with the invention, the viewedimage is less than the area of the projected image or beam and, in fact,substantially conforms or is slightly less'than the area of the image ofthe scene.

For actual framing adjustment, mirror 48 is pivotally mounted in theprojector as shown in FIG. 3. That is, mirror 48 is affixed to shaft 72which is, in turn, pivotally mounted in supports 74 and 76 and extendedthrough the side wall 78 of the viewer to a knob 80 which permits manualadjustment of the position of the mirror with respect to the lensassembly 44 and the screen 14. Hence, mirror 48 is mounted for angulardisplacement around an axis which is parallel to film 30 and in a planenormal to the longitudinal axis of the film such that rotation of mirror48 deflects optical axis 50 along the vertical axis of the screen 14.Stated otherwise, the mirror 48 is mounted to permit varying of theprojection path relative to the screen 14 in a plane 79 which bisectsthe screen and conforms to the longitudinal axis of projected image ofthe film frame. For economy and increased compactness of the unit, themirror 48 is trapezoidal shaped inasmuch as the beam cross section inthe plane of the mirror is narrower towards the rear of the viewer 10 inaccordance with the ever widening beam 45 and the angle of inclinationof the mirror to the beam axis 46.

Deflection of the optical path in this plane only is provided since onlylongitudinal framing of the recorded scenes is required in thisembodiment. The latter results from the fact that,.as shown in FIG. 4,the aperture or opening 43 of aperture plate 42 only exceeds the lengthof the scene as recorded, or that is, exceeds the length of the filmframes 82 while it substantially conforms to or is slightly less thanthe width of these scene frames. Consequently, as in conventionalprojector apparatus, the lateral margins 84 of the film frame 82 arepositioned in registration with the aperture 43, for example, by sidefilm guides (not shown) or other arrangements which align thelongitudinal axis of the film frames with the centerof the aperture.However, as previously indicated the latter exceeds the longitudinaldimension of the film frames 82 such that it does not frame theirlongitudinal margins or edges 88.

' It should be understood of course that the opening of the cassette l0and itspressure plate (not shown) must also provide an aperture whichexceeds the area of the recorded scene and, in fact, exceeds the area ofaperture 43 if the beam of light 45 is to be larger than the recordedscene at the plane of the film.

As shown in FIG. 4, the aperture 43 and the lens assembly 44 transmit animage of a film section 56 (conforming to the size of aperture 43) whichexceeds the length of the film frame 82 and the screens opaque border 70or at least its top and bottom edges 86 as shown in FIGS. 1 and 2functions to frame the longitudinal limits of the scene. Hence, the topand bottom edges 86 of the border 70 exclude transmission of the top andbottom portions 92 of the beam 45. Consequently, these border edges 86in cooperation with the adjustable mirror 48 are designed to effectivelyframe the projection of the recorded scene such that the viewed imagedoes not include light rays from film portions outside-of the fihn frame82.

For proper operation, the mirror 48 in all of its operational positionsis designed to be of sufficient area to intercept and redirect theentire beam 45 emanating from the projection lens 44 towards the screen14. Hence, the mirror 48 is made to exceed the beam dimension impingingon the mirror as measured on an axis 92 perpendicular to shaft 72 so asto permit mirror variation for the framing adjustment. The length of themirror, as measured along the axis 92 is, of course, related to theframe displacement required. Preferably, the overall length of themirror need be only about percent greater than the' length illuminatedby the beam when the mirror is'located at its center position since theangular variation necessary for framing is kept relatively small, e.g. afew degrees inasmuch as, the aperture 43 preferably only exceeds thelength of the useful portions of the image frame 82, as measured alongits longitudinal axis 90, by approximately 10 percent. This oversizedlength of the aperture 43 is generally sufficient to permit positioningof successive film frames within the aperture plate opening byconventional claw arrangement inasmuch as the film to film variationbetween the recorded images and the sprocket holes of the particularfilm as well as mechanical tolerances of conventional claw mechanismsetc. will generally be much less then 10 percent of the length of theimage frame.

In an exemplary embodiment, a projector housing having a front viewingface which includes an opaque border enclosing a rectangular transparentscreen approximately 18.3cm. high and 24.4cm. wide was employed.Disposed in the rear of the top surface of the apparatus was a cassettewell configured to accept a cassette of the described type and toposition it in operative relation with other elements of the housing. Inthis example, the cassette carried motion picture film having aplurality of image frames which measured about 0.57 cm. wide and 0.42cm. long, serially arranged along the length of the film strip. Mountedbeneath the cassette in operative arrangement with the projectionstation of the latter was an aperture plate having an opening whichmeasured about 0.53 cm. wide and 0.45 cm. long and a projection lenshaving a speed of H92 and 0,89cm. focal length which produced a tracklength of approximately 43 cm. from the film to the screen. Atrapezoidal mirror measuring approximately l0.lcm. along its base, by9.80m. along its top and 8.9cm. in height was positioned at the base ofthe projector cabinet approximately 12.7cm. below the film and pivotallymounted for rotation of approximately 4 about an axis parallel to boththe plane of the aperture plate and the screen. This projection systemproduced a projection image or beam height in the plane of the screenwhich measured about 22cm. high such that the screen border interceptedthe margins of the beam and permitted a framing adjustment along itsvertical axis. Those familar with the motion picture arts will readilyappreciate the novel and highly unique advantages of this inventionwhich provides a projection system having a simplified framingarrangement. In conjunction with projection of an elongated imageportion, the adjustable mirror which is adapted for image framingprovides a simplified viewer construction including an uncomplicatedshuttle arrangement which requires no alteration of its mechanism duringoperation. The latter eliminates possible film damage due to manualadjustments of the claw motion during projection operations.

It should be understood that this invention may be practiced or embodiedin still other ways without departing from the spirit of essentialcharacter thereof. Hence, the preferred embodiment wherein isillustrative and not restrictive, the scope of the invention beingindicated by the appended claims and all variations which come withinthe meaning of the claims are intended to be embraced therein.

What is claimed is:

l. A compact motion picture projection apparatus comprising a housing ofsubstantially opaquematerial, said housing including a transparentviewing screen providing a front surface of said housing, said screenbordered by a substantially opaque portion of said housing which portionforms a masking element disposed around the perimeter of said screen,means for receiving a strip of photographic film having a plurality ofsubstantially uniformly spaced perforations and a plurality ofsubstantailly uniformly spaced recorded scenes of given length arrangedalong the length of such film strip, such recorded scenes being locatedlongitudinally with respect to such perforations within a predetermineddistance so as to provide a predetermined scene-to-perforationtolerance, an aperture plate defining a projection plane locatedrearwardly of said screen and in adjoining relation to a top surface ofsaid housing, said aperture plate including an aperture substantiallyequal to the width of such recorded scenes and at least equal in lengthto the length of such recorded scenes plus such scene-to-perforationtolerance, means for progressively positioning each of such recordedscenes at such projection plane including shuttle means for cooperatingwith such perforations of said film strip so as to intermittentlyadvance such film strip and progressively locate incremental sections ofsuch film strip over said aperture, said shuttle configured forintermittently advancing each such perforation a predetermined distanceso as to progressively locate each such scene over said aperture at apoint within a predetermined distance equal to said perforation-to-scenetolerance such that the full length of each such scene is progressivelylocated within the length of said aperture, means for directing lightdownwardly through each scene and through said aperture along a downwardoptical path when such scene is located over said aperture so as ,toproject an image of said aperture including an image of such scene alongsaid given path, a reflector element located in said given path forredirecting such image forwardly along a second path to said screen,said masking element enclosing a screen area substantially equal inlength and width to the image of such scenes such that the maskingelement intercepts the image of said'aperture and precludes furthertransmission of portions thereof exceeding the length of the image ofsuch scene at said screen, said reflector element being pivotallymounted in said housing and configured for rotation around an'axissubstantially normal to the longitudinal axis of such image, and meanscoupled to said reflector element and extending exteriorly of saidhousing so as to be accessible to the operator of said apparatus forinitial pivotal adjustment of said reflector element during projectionoperation whereby such scene images may be positioned within saidmasking element and other portions of the image of said aperture aremasked from view.

1. A compact motion picture projection apparatus comprising a housing ofsubstantially opaque material, said housing including a transparentviewing screen providing a front surface of said housing, said screenbordered by a substantially opaque portion of said housing which portionforms a masking element disposed around the perimeter of said screen,means for receiving a strip of photographic film having a plurality ofsubstantially uniformly spaced perforations and a plurality ofsubstantailly uniformly spaced recorded scenes of given length arrangedalong the length of such film strip, such recorded scenes being locatedlongitudinally with respect to such perforations within a predetermineddistance so as to provide a predetermined scene-toperforation tolerance,an aperture plate defining a projection plane located rearwardly of saidscreen and in adjoining reLation to a top surface of said housing, saidaperture plate including an aperture substantially equal to the width ofsuch recorded scenes and at least equal in length to the length of suchrecorded scenes plus such scene-to-perforation tolerance, means forprogressively positioning each of such recorded scenes at suchprojection plane including shuttle means for cooperating with suchperforations of said film strip so as to intermittently advance suchfilm strip and progressively locate incremental sections of such filmstrip over said aperture, said shuttle configured for intermittentlyadvancing each such perforation a predetermined distance so as toprogressively locate each such scene over said aperture at a pointwithin a predetermined distance equal to said perforation-to-scenetolerance such that the full length of each such scene is progressivelylocated within the length of said aperture, means for directing lightdownwardly through each scene and through said aperture along a downwardoptical path when such scene is located over said aperture so as toproject an image of said aperture including an image of such scene alongsaid given path, a reflector element located in said given path forredirecting such image forwardly along a second path to said screen,said masking element enclosing a screen area substantially equal inlength and width to the image of such scenes such that the maskingelement intercepts the image of said aperture and precludes furthertransmission of portions thereof exceeding the length of the image ofsuch scene at said screen, said reflector element being pivotallymounted in said housing and configured for rotation around an axissubstantially normal to the longitudinal axis of such image, and meanscoupled to said reflector element and extending exteriorly of saidhousing so as to be accessible to the operator of said apparatus forinitial pivotal adjustment of said reflector element during projectionoperation whereby such scene images may be positioned within saidmasking element and other portions of the image of said aperture aremasked from view.